Re: [PATCH v2 2/2] riscv: KVM: add basic support for host vs guest profiling

[Quan Zhou <zhouquan@xxxxxxxxxxx>]

On 2024/8/21 20:51, Andrew Jones wrote:
> On Tue, Aug 13, 2024 at 09:24:10PM GMT, zhouquan@xxxxxxxxxxx wrote:
> > From: Quan Zhou <zhouquan@xxxxxxxxxxx>
> >
> > For the information collected on the host side, we need to
> > identify which data originates from the guest and record
> > these events separately, this can be achieved by having
> > KVM register perf callbacks.
> >
> > Signed-off-by: Quan Zhou <zhouquan@xxxxxxxxxxx>
> > ---
> >   arch/riscv/include/asm/kvm_host.h |  5 +++++
> >   arch/riscv/kvm/Kconfig            |  1 +
> >   arch/riscv/kvm/main.c             | 12 ++++++++++--
> >   arch/riscv/kvm/vcpu.c             |  7 +++++++
> >   4 files changed, 23 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> > index 2e2254fd2a2a..d2350b08a3f4 100644
> > --- a/arch/riscv/include/asm/kvm_host.h
> > +++ b/arch/riscv/include/asm/kvm_host.h
> > @@ -286,6 +286,11 @@ struct kvm_vcpu_arch {
> >   	} sta;
> >   };
>
> Let's add the same comment here that arm64 has unless you determine
> that 'any event that arrives while a vCPU is loaded is considered to be
> "in guest"' is not true for riscv.

Ok, i will add this comment to clarify the point.

Thanks,
Quan

> > +static inline bool kvm_arch_pmi_in_guest(struct kvm_vcpu *vcpu)
> > +{
> > +	return IS_ENABLED(CONFIG_GUEST_PERF_EVENTS) && !!vcpu;
> > +}
> > +
> >   static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> >   
> >   #define KVM_RISCV_GSTAGE_TLB_MIN_ORDER		12
> > diff --git a/arch/riscv/kvm/Kconfig b/arch/riscv/kvm/Kconfig
> > index 26d1727f0550..0c3cbb0915ff 100644
> > --- a/arch/riscv/kvm/Kconfig
> > +++ b/arch/riscv/kvm/Kconfig
> > @@ -32,6 +32,7 @@ config KVM
> >   	select KVM_XFER_TO_GUEST_WORK
> >   	select KVM_GENERIC_MMU_NOTIFIER
> >   	select SCHED_INFO
> > +	select GUEST_PERF_EVENTS if PERF_EVENTS
> >   	help
> >   	  Support hosting virtualized guest machines.
> >   
> > diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> > index bab2ec34cd87..734b48d8f6dd 100644
> > --- a/arch/riscv/kvm/main.c
> > +++ b/arch/riscv/kvm/main.c
> > @@ -51,6 +51,12 @@ void kvm_arch_hardware_disable(void)
> >   	csr_write(CSR_HIDELEG, 0);
> >   }
> >   
> > +static void kvm_riscv_teardown(void)
> > +{
> > +	kvm_riscv_aia_exit();
> > +	kvm_unregister_perf_callbacks();
> > +}
> > +
> >   static int __init riscv_kvm_init(void)
> >   {
> >   	int rc;
> > @@ -105,9 +111,11 @@ static int __init riscv_kvm_init(void)
> >   		kvm_info("AIA available with %d guest external interrupts\n",
> >   			 kvm_riscv_aia_nr_hgei);
> >   
> > +	kvm_register_perf_callbacks(NULL);
> > +
> >   	rc = kvm_init(sizeof(struct kvm_vcpu), 0, THIS_MODULE);
> >   	if (rc) {
> > -		kvm_riscv_aia_exit();
> > +		kvm_riscv_teardown();
> >   		return rc;
> >   	}
> >   
> > @@ -117,7 +125,7 @@ module_init(riscv_kvm_init);
> >   
> >   static void __exit riscv_kvm_exit(void)
> >   {
> > -	kvm_riscv_aia_exit();
> > +	kvm_riscv_teardown();
> >   
> >   	kvm_exit();
> >   }
> > diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> > index 8d7d381737ee..e8ffb3456898 100644
> > --- a/arch/riscv/kvm/vcpu.c
> > +++ b/arch/riscv/kvm/vcpu.c
> > @@ -226,6 +226,13 @@ bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
> >   	return (vcpu->arch.guest_context.sstatus & SR_SPP) ? true : false;
> >   }
> >   
> > +#ifdef CONFIG_GUEST_PERF_EVENTS
> > +unsigned long kvm_arch_vcpu_get_ip(struct kvm_vcpu *vcpu)
> > +{
> > +	return vcpu->arch.guest_context.sepc;
> > +}
> > +#endif
> > +
> >   vm_fault_t kvm_arch_vcpu_fault(struct kvm_vcpu *vcpu, struct vm_fault *vmf)
> >   {
> >   	return VM_FAULT_SIGBUS;
> > --
> > 2.34.1
>
> Thanks,
> drew